The present invention relates to a trocar that is inserted and placed in an incision to guide a surgical instrument when the surgical instrument is inserted in an affected area such as an eyeball through the incision made in the affected area, thereby preventing excessive load from being applied to the incision. The present invention also relates to a method for manufacturing the trocar.
Conventionally, a two-step method has been employed as a method for inserting and placing a cannula (insertion tube) in an eyeball. In the two-step method, an incision tool and a trocar equipped with a cannula are separately prepared. An incision is formed in the eyeball with an incision blade of the incision tool in advance. The incision tool is then replaced with the trocar, and the trocar is inserted in the eyeball through the incision. The cannula is inserted and placed in the eyeball by withdrawing an inner needle of the trocar. Thus, there is no need to insert and withdraw the incision blade of the incision tool through the cannula. Furthermore, by setting the width dimension of the incision blade to be slightly greater than the outer diameter of the cannula, the incision dimension of the incision can be set to be slightly greater than the outer diameter of the cannula. Thus, when the trocar is inserted in the eyeball, excessive load is prevented from being applied to the incision, and the incision is allowed to heal easily.
For example, Patent Document 1 discloses a method for inserting and placing a cannula (insertion tube) using a trocar through a one-step method. In the one-step method, a trocar is prepared in which an incision tool is inserted in the cannula in advance from its proximal end toward its distal end such that the incision blade of the incision tool projects from the distal end of the cannula. To insert the trocar into the eyeball, first, an incision is formed by the incision blade, and subsequently, the cannula is inserted into the eyeball through the incision. The incision blade is then withdrawn from the cannula. In this manner, the cannula is inserted and placed in the eyeball. In the one-step method, since insertion of the incision blade and the cannula into the eyeball is performed in a single continuous operation, the insertion operation of the trocar is easy compared with the two-step method.